1. Field of the Invention
This invention relates to a support structure for a cylinder, and particularly, a support structure which is very useful when applied in supporting a plate cylinder of a printing press.
2. Description of the Related Art
A conventional support structure for a plate cylinder of a printing press will be explained with reference to FIGS. 3 to 5. FIG. 3 is a side view showing a support structure on an operation side of a plate cylinder. FIG. 4 is a sectional view of FIG. 3. FIG. 5 is a side view showing a support structure on a drive side of the plate cylinder. As shown in FIGS. 3 and 4, an eccentric slide bearing 11a, which is a first eccentric bearing having an external diameter and an internal diameter different in axis position, is rotatably supported on a support frame 10a on the operation side. An outer race 12aa of an eccentric roller bearing 12a, which is a second eccentric bearing with different axis positions of the outer race 12aa and an inner race 12ab, is rotatably supported by the eccentric slide bearing 11a. The inner race 12ab of the eccentric roller bearing 12a supports an end portion of a shaft on the operation side of a plate cylinder 101. A fan-shaped dog 13a having a tooth space in an outer peripheral portion thereof is attached to an edge portion of the eccentric slide bearing 11a. The dog 13a is engaged with a pinion 14a, and the pinion 14a is rotated by a drive source (not shown). An annular plate 15 is attached to an end portion of the outer race 12aa of the eccentric roller bearing 12a. The annular plate 15 has the same dimensions as the internal and external diameters of the outer race 12aa, and has a flange 15a. 
As shown in FIG. 3, a casing 16 is attached to the support frame 100a. Inside the casing 16, a drive shaft 17 having an axis in a direction perpendicular to the axial direction of the plate cylinder 101 is rotatably supported. To the drive shaft 17, a worm wheel 18 is attached coaxially with the drive shaft 17. The worm wheel 18 is engaged with a worm gear 19. The worm gear 19 is rotated by a drive source (not shown). A base end portion (lower end portion) of a threaded shaft 20 is screwed to a front end portion (upper end portion) of the drive shaft 17. The threaded shaft 20 is rotatably supported by a support member 21 fixed to the support frame 100a. A base end portion of a connecting rod 22 is connected to a front end portion (upper end portion) of the threaded shaft 20. A front end portion of the connecting rod 22 is rotatably connected to the flange 15a of the annular plate 15 via a connecting pin 23. A rotary encoder 24 is connected to a base end portion (lower end portion) of the drive shaft 17. The annular plate 15, casing 16, drive shaft 17, worm wheel 18, worm gear 19, threaded shaft 20, support member 21, connecting rod 22, and connecting pin 23, which have been described above, constitute second rotating means in the present conventional example.
As shown in FIG. 5, an eccentric slide bearing 11b, which is the other first eccentric bearing having an external diameter and an internal diameter different in axis position, is rotatably supported on a support frame 100b on the drive side. An outer race 12ba of a roller bearing 12b, which has the outer race 12ba and an inner race 12bb consistent in axis, is rotatably supported by the eccentric slide bearing 11b. The inner race 12bb of the roller bearing 12b supports an end portion of a shaft on the drive side of the plate cylinder 101. A fan-shaped dog 13b having a tooth space in an outer peripheral portion thereof is attached to an edge portion of the eccentric slide bearing 11b. The dog 13b is engaged with a pinion 14b. The pinion 14b is connected to the drive source that drives and rotates the pinion 14a on the operation side, and can be rotated in the same amount as is the pinion 14a on the operation side. These dogs 13a, 13b, the pinions 14a, 14b, and the drive source, which have been described above, constitute first rotating means in the present conventional example. The reference numeral 102 denotes a blanket cylinder.
According to the foregoing support structure, when the drive source is actuated to rotate the pinions 14a, 14b in the same amount, the eccentric slide bearings 11a, 11b are rotated via the dogs 13a, 13b. As a result, the axes Oa, Ob of the plate cylinder 101 move about the eccentric axes Oa1, Ob1 of the eccentric slide bearings 11a, 11b via the roller bearings 12a, 12b. Thus, the distance between the axes O, O of the blanket cylinder 102 and the axes Oa, Ob of the plate cylinder 101, namely, the distance between the outer peripheral surfaces of the blanket cylinder 102 and the plate cylinder 101 can be changed. By this measure, an object to be printed, such as a sheet, can be printed at an appropriate printing pressure in accordance with, for example, the thickness of the object to be printed. When the worm gear 19 is rotated to rotate the worm wheel 18, the drive shaft 17 rotates. In accordance with the rotation of the drive shaft 17, the threaded shaft 20 ascends or descends. As a result, the annular plate 15 rotates via the connecting rod 22 and the connecting pin 23, whereupon the outer race 12aa of the eccentric roller bearing 12a rotates. Thus, the axis Oa on the operation side of the plate cylinder 101 moves about the eccentric axis Oa2 of the eccentric roller bearing 12a via the inner race 12ab. That is, the axis Oa on the operation side of the plate cylinder 101 can be displaced relative to the axis of the blanket cylinder 102 about the axis Ob on the drive side of the plate cylinder 101. By this measure, displacement of the printing position in accordance with a change, for example, in the thickness of the object to be printed, such as a sheet, can be corrected.
In the above-described support structure, the second rotating means is connected only to the eccentric roller bearing 12a on the operation side of the plate cylinder 101. Thus, if it is attempted to adjust the printing pressure by actuating the first rotating means as stated earlier, rotation of the eccentric roller bearing 12a on the operation side of the plate cylinder 101 is restrained by the second rotating means. As a result, a difference arises between the amount of movement of the axis Oa on the operation side of the plate cylinder 101 and the amount of movement of the axis Ob on the drive side of the plate cylinder 101. This results in cocking of the plate cylinder 101.
The present invention has been accomplished to solve the above-described problem.
According to the present invention, there is provided a support structure for a cylinder, comprising:
a pair of frames;
a pair of first eccentric bearings rotatably supported on the frames;
a pair of second eccentric bearings rotatably supported by the first eccentric bearings and rotatably supporting end portions of a shaft of the cylinder;
first rotating means for rotating the first eccentric bearings relative to the frames in a same amount;
second rotating means for rotating one of the second eccentric bearings relative to one of the frames; and
restraining means for restraining rotation of the other second eccentric bearing relative to the other frame.
In the above support structure, the restraining means may have a connecting rod having one end portion rotatably connected to the other second eccentric bearing, and having the other end portion rotatably connected to the other frame.
According to the cylinder support structure of the present invention, the restraining means restrains rotation of the other second eccentric bearing. As a result, the one second eccentric bearing and the other second eccentric bearing move in the same manner. Thus, there is no difference between the amount of movement of the axis at one end portion of the cylinder and the amount of movement of the axis at the other end portion of the cylinder. Consequently, no cocking occurs in the cylinder.